Keep a stiff upper lip
Remain resolute and unemotional in the face of adversity, or even tragedy.
This is such a clichéd expression that it is difficult to imagine doing anything else with a stiff upper lip apart from keeping it. It is similar to 'keep a straight face', 'keep you chin up', and (to the amusement of many Americans) 'keep you pecker up'. The phrase has become symbolic of the British, and particularly of the products of the English public school system during the age of the British Empire. In those schools the 'play up and play the game' ethos was inculcated into the boys who went on to rule the Empire. That 'do your duty and show no emotion' feeling was expressed in Alfred, Lord Tennyson's The Charge of the Light Brigade:
"Forward, the Light Brigade!"
Was there a man dismay'd?
Not tho' the soldier knew
Someone had blunder'd:
Their's not to make reply,
Their's not to reason why,
Their's but to do and die:
Into the valley of Death
Rode the six hundred.
In more recent years British heroes have been able to show more emotion. Footballers now cry when they lose and the public don't turn away - that would have been unthinkable before WWII. The national outpouring of grief at the death of Princess Diana, although intensified by a media frenzy, began a trend toward accidental deaths being commemorated with garlands of flowers laid by the public.
As recently as 1963 P. G. Wodehouse published a novel called 'Stiff Upper Lip, Jeeves', and you can't get much more English than that. It is strange then that a phrase so strongly associated with the UK should have originated in America. The first printed reference to it is in the Massachusetts Spy, June 1815:
"I kept a stiff upper lip, and bought [a] license to sell my goods."
That citation, although it doesn't explicitly refer to keeping one's emotions in check, is similar to several US references from the 19th century which do make the meaning unambiguous; for example, from the Huron Reflector, 1830:
"I acknowledge I felt somehow queer about the bows; but I kept a stiff upper lip, and when my turn came, and the Commodore of the P'lice axed [sic] me how I come to be in such company... I felt a little better."